| The meltblowing process was originally developed to produce filament webs for filtration media. In this process, fine filaments (∼1 μm) are produced by attenuating extruded polymer streams through the action of high velocity airflow. These filaments are laid randomly to form a web. Historically, researchers have used empirical approaches to alter process and material parameters to obtain desirable final product properties. Few studies have used a fundamental approach to infer the combined influence of intrinsic material characteristics, dynamics of fiber formation, and web formation on the properties of the product.; The purpose of this work is to provide a first step in establishing “material-process-property” in meltblowing. It is realized through a fundamental approach to determine the deformation and evolution of morphology in meltblown filaments. The framework that has been developed for this purpose combines the kinematics of deformation of the viscoelastic polymer with stress-induced crystallization in order to gain an understanding of how structure and properties evolve in this process. Such an approach could provide a window and a direction for new products through polymer development and process changes.; Our approach has two main parts: (1) An experimental analysis of the structure and properties of meltblown filaments, comprising of diameter, crystallinity and orientation profiles of meltblown polypropylene filaments that were obtained through scanning electron microscopy, x-ray diffraction, differential scanning calorimetry and Raman spectroscopy. (2) A model for the dynamics and the evolution of structure in a meltblowing process. Predictions of the model are discussed in the context of experimental data on meltblowing of polypropylene, obtained from both in-house experiments and published literature. The results show much promise for the development of a rational quantitative model of the threadline in a meltblowing process, similar to the models that have served to advance melt spinning over the last five decades. |
